I've been following SharpDevelop for years. While I really liked the features SD had that VS was missing (like automatically adding using statements), the things it lacked (VS had better document formatting) always had me going back to VS.
I'm strongly encouraged by what i'm seeing in SD5. Also helping SD in my mind is that i'm one of probably many .Net developers that felt ditched (because we were) by MS after buying heavily into WPF and Silverlight and are now much more open to non-MS solutions.
I'm looking forward to coming back to SD - at least while i'm still using .Net :)